One of the tricks to building drama in a game is to make startling revelations to the characters. If they break into the office of an evil corporate executive to rifle through documents in the safe, they might find shocking evidence that he is the real father of one of the PCs. If they dig up the grave of the serial killer who died ten years ago to do some forensic work on the body, they may be startled to find the coffin is empty. If investigating the evil vizier on suspicion of kidnapping the sultan's daughter, they may discover the sultan himself has abducted her for some unspeakable demonic ritual and the vizier is actually trying to save her.

For even greater impact, drop something like this on the characters during combat.

Transcript

Leia: Come on guys, get it together!R2-D2: Well fine, I guess I'll just call in the cavalry.R2-D2: {sotto voce} Let's see, where did I leave my space dreadnought... Oh, that's right...[SFX]: < bebebing dooby ping doop pip-deep >[SFX]: Kaboom!GM: Luke, the only fighters left are you, Biggs, and Wedge.Luke: Great, the yokel and the psychopath.Wedge: Now now, good buddy. Just because I'm a shapeshifter doesn't mean I'm a yokel.Biggs: And shucks, Luke, just 'cos y'all didn't read the profiles don't make ya a psychopath now.Luke: Wait, wait, wait. Wedge is a shapeshifter?Biggs: A who with the what now?Luke: So who the hell is he, really?C-3PO: Shapeshiftist!Leia: All you need to know is he's a rebel, a damn good pilot, and about to become Red Squadron Leader if you're not careful!Luke: That's exactly what I'm afraid of!
{beat}Darth Vader: Don't mind me. Just lining up my shot.